Indeed, conservationists have suggested starting a "blue list" of species that have come back from the brink, mirroring the International Union for Conservation of Nature Red List of endangered species.

Lest we forget those success stories, we present our favourite five revivals.

Then in 1981, a population was discovered in Wyoming. It declined rapidly from disease, and by 1986 only 18 were left. All were captured and a fresh population was bred in captivity for a few years before being reintroduced to the wild in 1991.

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Blue iguana

Lowest recorded population: 15 in the wild

It's ironic that one of the most threatened species, blue iguanas, may be the longest-lived lizard in the world: the oldest individual made it to 67. At 1.5 metres long, including the tail, they can change their skin colour from camouflage grey to intimidating blue when they need to signal their presence.

They have been hunted for years by feral cats and dogs, which were introduced by humans to their Caribbean island home, Grand Cayman. By 2002, there were only 15 left (PDF).

Pink pigeon

Lowest recorded population: 10

On the island of Mauritius in the Indian Ocean lives the rarest pigeon in the world. The pink pigeon Nesoenas mayeri now numbers over 350, but that is the result of over two decades of conservation work.

At 38 centimetres long it is large for a pigeon, and its feathers are a predictable colour. Its major problem has been habitat loss, and it was not helped by the introduction of predatory monkeys. By 1990 there were only 10 pink pigeons left, all nesting in the same grove of trees.

Bali starling

Lowest recorded population: six

Most of this bird's problems can be attributed to its beauty. Because of its striking appearance – brilliant white, with blue skin around its eyes and black tips to its wings and tail – it is hugely popular in the caged-bird trade, and as a result is a prime target for poachers.

Leucopsar rothschildi lives only on the island of Bali in Indonesia. The population was down to 15 in 1990, bounced back to around 50 thanks to conservation efforts, then crashed to six in 2001 because of poaching.

Pedder galaxias

In 1972, amid a storm of protest, Lake Pedder in Tasmania, Australia, was flooded to drive a hydroelectric dam. Among the casualties was this blotchy-looking fish, which lived only in the lake.

It was last seen there in 1996, and by all accounts that population has been completely wiped out. But by the time this happened, the species had already been saved.

A few individuals were bred in captivity, and the fish were introduced to two nearby lakes. The population in Lake Oberon, where they were introduced in 1992, is thriving. A second group, introduced to Strathgordon Dam in 1997, has survived but is so far failing to breed.